The invention concerns a device for separation of media into their components through density centrifugation in a separation chamber, with an arrangement for detection and adjustment of the phase boundary between at least two optically differentiable fractions of the medium (phase detector), consisting of a light source, which illuminates the separation chamber in the region of the self-adjusting phase boundaries, of a light receiving arrangement, and optics, which reproduce a specific section of the region on the light receiving arrangement, which responds to different light signals according to optical differences between the fractions, and of a control circuit, connected downstream from the light receiving arrangement, to trigger control signals.
Such a device is known, for example, from U.S. Pat. No. 4,724,317 and from DE-A 33 01 113 (=EP-B 0 116 716). The media in question are primarily body fluids, in particular, blood.
The arrangement for detection and adjustment of the phase boundary in such devices, the phase detector, is supposed to improve the separation performance of the separation device. For this, the known arrangement uses the different light permeability of the individual fractions of the medium. For this purpose, the light source and the light receiving arrangement are disposed with the optics such that the optics are impacted by the light which passes through the fractions and is weakened differently by the differing absorption in the individual fractions. Based on the relationship of the light signals, the phase boundary is specified or other procedures are triggered.
In such an arrangement it is disadvantageous that the specification of the phase boundary or the generation of other control signals takes place solely on the basis of a light-dark differentiation, such that it is possible neither to differentiate between the individual fractions which are impermeable to light nor to use a separation device equipped with such a phase detector with blood plasma which is highly turbid due to the donor's condition.
The above problems are avoided with an arrangement according to U.S. Pat. No. 4,493,691. In this arrangement, a TV camera is provided, which records the image visible through the transparent rotor of the separation chamber and reproduces it on a TV display. The adjustment of the position of the phase boundary is performed manually by a human operator.
Manual adjustment of the phase boundary based on visual observation of the phase boundaries entails significant disadvantages. The accuracy of the detection system is limited by the visual limitations of the human eye as well as the limitations of the TV technology itself. Furthermore, the presence of a trained person is essential during the entire operation of the separation device. This conventional method is thus less than optimal and can be performed only with high technical and personnel expenditure.
The object of the invention is, starting from the device mentioned in the introduction, to refine it with a phase detector which automatically detects and adjusts the phase boundary such that it has differentiated detection capability and adjustment behavior and thus increases the potentials for use of the separation device along with greatly improved separation performance.